The injection of the dilution air into a combustion chamber of a gas turbine takes place preferably downstream of the burner.
CO emissions of gas turbine engines need reductions for the sake of saving the environment. Such emissions are known to appear, when there is not sufficient time in the combustion chamber to ensure the CO to CO2 oxidation, and/or this oxidation is locally quenched due to contact with cold regions in the combustor. Since firing temperatures are smaller under part load conditions CO and the CO to CO2 oxidation gets slower, thus CO emissions usually tend to increase under these conditions.
Besides low emissions a stable combustion process has to be assured. The combustion process in such gas turbines can lead to dynamic coupling. Such a dynamic or thermo acoustic coupling of gas turbine can combustors or in annular combustors may lead to strong pulsations in particular to strong low frequency pulsations, which negatively affect the stability and lifetime of the combustor. This may lead to reduced lifetime or in extreme cases to a mechanical failure of the gas turbine. In order to mitigate thermo acoustic pulsations usually dampers or resonators are installed in the combustion chamber and/or staging of the fuel supply is done as described for example in the US2010/0313568. Since low frequency dampers require large volumes this solution is not favoured. Fuel staging has a detrimental impact on the emission performance due to the creation of local hot spots (leading to NOx emissions) and local cold spots (leading to additional CO emissions).
A reduction of CO emissions in turn might be invested in lowering the gas turbine load at the parking point of a gas turbine. This reduces the environmental impact due to reduced CO2 emissions and overall cost of electricity due to less fuel consumption during engine parking.